My guess is that in most cases it would be cheaper (in the short term) to simply have a train employee stand in from of the train distributing money for the rob

My guess is that in most cases it would be cheaper (in the short term) to simply have a train employee stand in from of the train distributing money for the robbers to walk away. Of course, long term that would have an awful ROI. The robbers would return every time, and more robbers would join them.